A curious combination, isn't it? Avangi and I had a discussion about these kinds of
would
in another thread. I sense that there are two paradigms here,
only one of which is the "traditional" or "proper" conditional,
alternating between
will and
would.<>
1.
If we have it, it will be on the second shelf.
If we had it, it would be on the second shelf.
The second paradigm has what may be called the would of probability, alternating between would and would have.
2.
If we have it, it would be on the second shelf. (= If ..., (it seems to me that) it is probably on the second shelf)
If we had it, it would have been on the second shelf. (= If ..., (it seems to me that) it was probably on the second shelf)
Perhaps should and should have can even be used in this pair.
___________
On the other hand, it's all very mysterious; I may just be imagining things! 
CJ